| HS Code | 610338 |
| Product Name | Sodium Alginate |
| Chemical Name | Sodium alginate |
| Cas Number | 9005-38-3 |
| Molecular Formula | (C6H7NaO6)n |
| Molecular Weight | Polymer-dependent; repeating unit 198.11 g/mol, typical polymer range 10,000–600,000 g/mol |
| Appearance | White to yellowish-brown powder or granules |
| Odor | Slightly characteristic, almost odorless |
| Solubility | Soluble in water forming a viscous colloidal solution; insoluble in alcohol, ether, and chloroform |
| Ph 1 Percent Solution | 6.0–8.0 |
| Viscosity 1 Percent Solution | 20–2000 mPa·s at 25°C depending on grade |
| Gelation Mechanism | Forms a thermally irreversible gel in the presence of divalent cations, especially calcium ions |
| Bulk Density | Varies by grade; typical tapped bulk density 0.5–0.8 g/cm³ |
| Moisture Content | ≤15% by weight typical commercial specification |
| Heavy Metals As Lead | ≤20 mg/kg |
| Arsenic As As | ≤2 mg/kg |
| Lead As Pb | ≤5 mg/kg |
| Total Plate Count | ≤1000 CFU/g typical microbiological specification |
As an accredited Sodium Alginate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sodium Alginate, 500 g white to yellowish powder, packaged in a sealed amber glass jar with moisture-proof lid. |
| Container Loading (20′ FCL) | 20′ FCL loading of Sodium Alginate in sealed drums on pallets, securely lashed, moisture-protected, with proper labeling and safe handling. |
| Shipping | Sodium Alginate ships as a non-hazardous, moisture-sensitive powder in sealed bags or drums, protected from humidity and contamination. It should be transported in clean, dry containers, away from incompatible materials. Standard freight is suitable, with proper labeling and documentation for non-dangerous goods. |
| Storage | Store sodium alginate in a cool, dry place in an airtight, tightly sealed container, away from direct sunlight and moisture. Protect it from high humidity, as the powder is hygroscopic. Keep at room temperature, avoid heat sources, and handle with clean utensils. Properly stored, it remains stable for years. |
| Shelf Life | Sodium Alginate has a shelf life of about two years when stored cool, dry, and protected from sunlight. |
Reactive dye printing of cellulosic woven textiles uses sodium alginate as a low-solids thickener because the carboxyl groups are ionized under alkaline print conditions, creating negative surface charge that repels anionic reactive dye molecules and reduces dye fixation in the thickener film. The stock paste is hydrated at 4–8% (w/w) in demineralized water below 25°C using a high-shear disperser at 800–1,500 rpm for 45–90 minutes, then matured for 4–8 hours until viscosity stabilizes between 25,000 and 45,000 mPa·s at 25°C measured on a Brookfield RV spindle 6 at 20 rpm. After vacuum deaeration at −0.8 bar to −0.9 bar, 30–50% of the stock paste is combined with reactive dye, urea at 10–15% of print paste, and sodium bicarbonate at 1.5–3.0%, yielding a final sodium alginate concentration of 0.8–2.5% in the print paste. The mixed paste is applied through 80–125 mesh rotary screens, where shear rates in the 103–105 s−1 range temporarily reduce viscosity; low-viscosity grades with a controlled mannuronic-to-guluronic acid ratio recover sufficient viscosity between 5 s and 15 s after screen contact to prevent edge bleed. Drying is carried out at 100–110°C, followed by saturated steam fixation at 101–103°C for 8–10 minutes to covalently fix reactive dye to cellulose; cold rinse, hot wash at 60–90°C, and soaping remove unfixed dye and alginate residues. Process water hardness above 100 ppm CaCO₃ must be chelated with polyphosphate or EDTA to prevent calcium-induced gel specks, and mixing vessels must be stainless steel or plastic-lined because carbon steel corrosion can release iron and calcium into the paste. Regulatory compliance for exported printed textiles includes REACH (EC) No 1907/2006 substance registration, ZDHC MRSL V3.1 exclusions for surfactants and solvents, Oeko-Tex Standard 100 Annex 4 finished-article residue limits, and ISO 105-C06:2010 wash fastness testing on the printed garment or panel. Finished textiles exiting this process include woven cotton shirting, viscose challis apparel fabric, and home textile panels.
Sodium alginate functions as an aqueous electrode binder in silicon-containing graphite anode slurries, where its carboxylic acid groups form hydrogen-bonded networks with surface silanol groups on silicon particles and restrain aggregate movement during lithiation-induced volume change. The binder is introduced at 1–3% of dry anode solids, while silicon active material constitutes 10–30% of the anode active mass, carbon black is added at 1–3%, and deionized water is adjusted to a final slurry solids content of 55–65% for slot-die coating. In production-scale cell lines, the slurry is mixed in a vacuum planetary mixer at 1,500–2,500 rpm under −0.08 MPa to −0.09 MPa vacuum; the vessel and transfer piping are specified as 316L stainless steel because slurry pH below 6.5 can etch copper foil and pH above 7.5 can destabilize the alginate network through chain degradation. The slurry is coated onto copper foil of 8–12 µm thickness using a slot-die coater at 5–15 m/min, dried in a multi-zone air-float oven at 70–90°C, and calendered to an electrode porosity of 35–40% before slitting. Process water calcium must remain below 50 ppm, and shear history above 104 s−1 should be limited because excessive polymer chain scission reduces slurry thickening and final coating adhesion. Compliance for assembled cells includes EU Battery Regulation (EU) 2023/1542, UN 38.3 transport testing, and IEC 62619:2022 safety requirements for industrial cells. The resulting cell formats are high-energy-density lithium-ion pouch cells and cylindrical cells for electric vehicle and power tool applications. Published cycle-life data at cell level vary with silicon content, electrolyte formulation, and calendering pressure; site-specific validation under production temperature and pressure conditions is required.
| Component | Range | Function | Production control point |
|---|---|---|---|
| Silicon-graphite active material | 70–95 wt% of dry anode solids | lithium storage host | silicon fraction 10–30% of active mass |
| Sodium alginate binder | 1–3 wt% of dry anode solids | particle-copper adhesion and swelling restraint | water calcium <50 ppm; pH 6.5–7.5 |
| Carbon black | 1–3 wt% of dry anode solids | electron percolation network | fineness of grind <25 µm |
| Deionized water | to 55–65% total slurry solids | solvent carrier | conductivity <5 µS/cm |
Dental alginate impression powders are dry blends in which sodium alginate at 10–15 wt% acts as the irreversible hydrocolloid former, calcium sulfate dihydrate at 12–16 wt% supplies calcium ions, and sodium phosphate at 2–3 wt% acts as a set retarder. The powder is mixed with water at a 1:2 to 2:3 powder-to-water ratio for 30–45 seconds; the mixed paste must demonstrate a setting time of 1.0–2.5 minutes at 23°C and a recovery from deformation of at least 92% under ISO 1563 test conditions. Production is dry blending in a low-shear ribbon mixer to avoid premature calcium release, filling into moisture-barrier laminated pouches below 40% RH, and sterilization only for medical grades that require it. In wound dressing fiber production, a 3–6 wt% sodium alginate dope in deionized water is filtered, deaerated, and extruded through spinnerets into a 2–5% calcium chloride coagulation bath; the resulting calcium alginate filaments are drawn, washed, air-dried, and needlepunched into nonwoven dressings. Finished articles produced under these standards are irreversible hydrocolloid dental impression trays for crown and bridge prostheses, calcium alginate wound dressings with high exudate absorptive capacity, and nasal or sinus packing. Compliance includes ISO 1563 for dental alginate impression materials, European Pharmacopoeia monograph Sodium Alginate for pharmaceutical raw material purity and viscosity limits, and EN 13726-1:2002 for primary wound dressing absorptive capacity. Operational limitations include viscosity collapse after storage above 30°C in humid environments and premature gelation if the powder blend picks up moisture above 0.5% during filling.
Covered electrode manufacturing uses sodium alginate as a binder and extrusion plasticizer in the wet flux coating that is applied around carbon steel core wire. The addition ratio is 0.3–1.0% of dry flux formulation by weight; higher levels above 1.5% lead to coating cracks after drying and erratic arc starts because sodium vaporizes during arc ignition, while levels below 0.2% produce poor green strength and slumping during transport through the drying line. In a typical production sequence, rutile, calcium carbonate, cellulose powder, ferroalloy powders, and sodium alginate are dry-mixed in a ploughshare mixer for 10–20 minutes, then wet-mixed with 18–25% water by total flux weight until a ductile mass forms. The wet flux is extruded onto cleaned core wire of 0.8–4.0 mm diameter in a single-screw extruder with barrel pressure maintained between 8 MPa and 12 MPa; coating concentricity is held within ±0.03 mm using multi-axis laser gauging. Drying is staged at 60–80°C for 2–4 hours to remove surface water, followed by 110–120°C until coating moisture is below 0.3% to prevent weld metal hydrogen pickup. The coated electrodes are classified as rutile-type covered electrodes for manual metal arc welding of carbon steel under AWS A5.1/A5.1M:2012 E6013 and equivalent ISO 2560:2023 rutile designations. Process water must contain less than 100 ppm calcium to avoid localized alginate coagulation, and mixing temperature must remain below 40°C to prevent thermal thinning of the flux paste.
Cold-set gelation with sodium alginate is used in restructured protein matrices and liquid-core encapsulation because the polymer forms a three-dimensional network only in the presence of free calcium ions, allowing unmixed or prepumped systems to remain fluid before shaping. The addition ratio is 0.5–1.0% for restructured meat or fish, 0.4–0.8% for plant-based fibrous analogues, and 0.2–0.5% for ice cream stabilizer systems. In a typical restructuring line, sodium alginate is dispersed in chilled process water at 5–10°C using a high-shear mixer, hydrated for 30–60 minutes, and then mixed with meat or protein paste; calcium lactate or calcium sulfate is injected or blended at 0.1–0.3% immediately before forming, after which the matrix sets at 4°C over 10–30 minutes. For liquid-core encapsulation, the alginate solution at 0.8–1.5% is dripped or jet-cut into a 2–5% calcium chloride bath; bead size is controlled by nozzle diameter, vibration frequency, and bath residence time. The resulting food outputs are restructured fish fillets, plant-based striated protein analogues, dessert gel beads, and edible moisture-barrier films. Compliance includes FDA 21 CFR 184.1724 for sodium alginate as GRAS, EU Regulation (EC) No 1333/2008 food additive E401, and the Joint FAO/WHO Expert Committee on Food Additives monograph for alginic acid and its ammonium, calcium, potassium, and sodium salts. Operational limits apply below pH 3.5, where acid-catalyzed hydrolysis shortens gel life, and above 80°C, where prolonged heating can depolymerize the alginate chain; calcium ion availability must be buffered with sodium citrate where the food matrix contains high native calcium or magnesium.
Paper surface treatment with sodium alginate reduces air permeability and oil penetration on greaseproof packaging by forming a continuous film at the size press; a 0.5–1.5 wt% aqueous solution is prepared at 60–70°C and applied at 0.5–2.0 kg dry alginate per tonne of paper using a metered size press or air-knife coater before drying at 90–110°C and light calendering, with compliance under FDA 21 CFR 176.170 for components in contact with aqueous and fatty foods, EU Regulation 1935/2004 for food-contact materials, and ISO 8791-4 for Parker Print-Surf roughness of the finished substrate; terminal product types are greaseproof wrapping paper, release base paper, and coated inkjet media.
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Sodium alginate is the sodium salt of alginic acid, a linear polysaccharide composed of 1,4-linked β-D-mannuronic acid and α-L-guluronic acid residues extracted from brown algae such as Laminaria hyperborea, Macrocystis pyrifera, and Ascophyllum nodosum. The material is assigned the additive designation E401 under European Commission Regulation 1333/2008 Annex II and is affirmed as GRAS for direct food use under FDA 21 CFR 184.1724. The primary technical functions are thickening, ionic gelation, film formation, and suspension stabilisation across food, pharmaceutical, textile, dental, and biotechnological processing. Commercial product descriptions are supplier-specific rather than governed by a universal model system; grade codes typically encode viscosity class, average molecular weight, particle mesh, and mannuronic/guluronic acid ratio. The product is supplied as a cream-to-light-brown powder with cold-water solubility, anionic charge density, and the capacity to form thermostable gels in the presence of divalent cations.
Specification boundaries for sodium alginate are established through rotational viscometry, drying balance, pH determination, and heavy-metal analysis. A 1% aqueous solution measured with a Brookfield LV rotational viscometer at 20 °C is the most common supplier-defined basis for low-, medium-, and high-viscosity designations. Supplier model designations such as LV, MV, HV, and HG are not harmonized across producers and must be read against the certificate of analysis. M/G ratio is determined by 1H NMR or high-performance anion-exchange chromatography with pulsed amperometric detection; the ratio controls calcium sensitivity and gel texture more directly than molecular weight alone. Food and pharmaceutical monographs impose additional limits for loss on drying, total ash, lead, arsenic, and microbial quality.
| Parameter | Method/Equipment | Low-viscosity grade | Medium-viscosity grade | High-viscosity grade |
|---|---|---|---|---|
| Viscosity of 1% solution at 20 °C | Brookfield LV, ASTM D2196-20 | 20–200 mPa·s | 200–600 mPa·s | 600–1500 mPa·s |
| pH of 1% solution | USP 791 | 6.0–8.0 | 6.0–8.0 | 6.0–8.0 |
| Loss on drying | USP 731, 105 °C | ≤15% | ≤15% | ≤15% |
| Residue on ignition | USP 281 | 18–27% | 18–27% | 18–27% |
| Lead | FCC Sodium Alginate monograph | ≤2 mg/kg | ≤2 mg/kg | ≤2 mg/kg |
| Arsenic | FCC Sodium Alginate monograph | ≤3 mg/kg | ≤3 mg/kg | ≤3 mg/kg |
| Particle size | Air-jet sieve | ≥95% through 80 mesh (180 µm) | ≥95% through 200 mesh (75 µm) | ≥95% through 200 mesh (75 µm) |
Viscosity is not a single-point intrinsic constant. Because sodium alginate solutions are shear-thinning, the reported value depends on spindle speed, concentration, temperature, and ionic background. A medium-viscosity grade read at 60 rpm can appear 40–60% lower than the value obtained at 12 rpm; specification comparisons therefore require identical rotational shear conditions. In dry handling, material transferred under relative humidity above 60% absorbs moisture rapidly, cakes in hoppers, and requires pre-drying before vacuum conveying. Operators of continuous mixing systems also observe fish-eye agglomerates when dry powder is added without a pre-blend, fouling plate heat exchangers and pump strainers.
Unlike thermally gelled hydrocolloids, sodium alginate forms an ionically crosslinked network through the chelation of Ca²⁺ between adjacent guluronic acid blocks. High-G grades containing 60–75% guluronic acid produce short, brittle gels with higher storage modulus; high-M grades produce softer, more elastic gels. Gelation occurs without heating and is largely irreversible on reheating, but the resulting gel is not a melt-set network. In continuous sauce and dessert lines, direct injection of calcium chloride into a hydrated alginate solution above 20 mM free Ca²⁺ can induce instantaneous heterogeneous gelation, blocking static mixers and tubular heat exchangers. Production-scale mixing therefore uses delayed-release calcium salts, sequential addition under a rotor-stator mixer, or sequestrants such as tetrasodium pyrophosphate. Dry powder is pre-blended with 3–5 parts of sucrose or dispersed in 5–10% ethanol to prevent fish-eye agglomerates; a vortex created by an inline rotor-stator mixer at 3000 rpm is typical. The pH window for stable solutions is 4.0–10.0. Below pH 3.5, alginic acid precipitates; above pH 10 at temperatures above 60 °C, β-elimination causes rapid viscosity decay. The dry product is hygroscopic and should be stored at 25 °C and <65% relative humidity in sealed polyethylene-lined containers. Incompatibilities include high-concentration calcium salts, strongly acidic syrups, and oxidizers that depolymerize the chain; published data for specific continuous-line configurations is limited and must be verified with pilot-scale trials.
Process selection differs sharply from gelatin or agar. Gelatin requires cooling below 30–35 °C to set and loses network structure at body temperature; agar requires hydration at 90–95 °C, sets at 35–45 °C, and remelts near 85–95 °C. Sodium alginate can form a gel without a boiling step and remains gelled at temperatures that would melt gelatin, although prolonged retort exposure at 121 °C can reduce molecular weight and weaken gel strength. In restructured fruit and heat-stable bakery fillings, sodium alginate is dosed at 0.3–0.8% with a calcium source. Direct replacement of gelatin is not mass-equivalent: gel texture depends on calcium release rate, G-block content, and alginate concentration. Low-methoxyl pectin also gelates with Ca²⁺ but normally requires pH values below 3.5 for acidified fruit systems; sodium alginate operates above pH 4.0. κ-Carrageenan forms potassium-induced thermoreversible gels with high syneresis; xanthan does not form a true gel alone and requires a galactomannan. Table 2 summarises the comparative gating conditions.
| Hydrocolloid | Primary gel trigger | Thermal reversibility | Key limiting condition |
|---|---|---|---|
| Sodium alginate | Ca²⁺ ions, 0.1–0.5% CaCl₂ | Thermoirreversible; depolymerizes on prolonged retort | pH 4.0–10.0; direct concentrated Ca²⁺ addition causes heterogeneous gelation |
| Agar | Heat-set on cooling after 90–95 °C hydration | Remelts 85–95 °C | High syneresis; brittle gels |
| Gelatin | Cold-set 10–15 °C | Melts 30–35 °C | Animal origin; melts below body temperature; acid instability |
| Low-methoxyl pectin | Ca²⁺ set | Thermostable | Requires pH 2.8–3.5 in many formulations |
| κ-Carrageenan | K⁺ ion set | Thermoreversible | High syneresis; potassium sensitivity |
| Xanthan | No true gel alone | Shear-reversible viscosity only | Requires galactomannan for gelation |
Within the alginate family, sodium alginate differs from alginic acid, calcium alginate, and propylene glycol alginate. Alginic acid is water-insoluble at pH below 3.0 and is used as a tablet disintegrant; calcium alginate is water-insoluble and is produced as fiber for wound dressings, where gelation occurs by ion exchange with sodium-rich exudate. Propylene glycol alginate is esterified and remains soluble in acidified dairy, fruit, and beer foam systems where sodium alginate precipitates. Sodium alginate is selected for neutral-pH thickening, ionic gelation, and pharmaceutical matrix applications; propylene glycol alginate is selected for acid stability and foam control.
Dental-grade sodium alginate is compounded with calcium sulfate dihydrate, tetrasodium pyrophosphate retarder, and fillers to produce an irreversible hydrocolloid impression material. Mixing with water at 23 °C produces a calcium-crosslinked gel with working time typically 1.5–3 min and setting time 3–5 min, depending on retarder concentration. ISO 1563 specifies elastic recovery, dimensional change, and compressive strength; production batches are evaluated for strain in compression and compatibility with dental stone. High ambient temperature shortens working time; powder exposure to moisture before mixing causes lump formation and variable set.
Pharmaceutical-grade sodium alginate is used as a hydrophilic matrix former and suspending agent. The USP-NF Sodium Alginate monograph and Ph. Eur. 0625 define identity, pH, loss on drying, total ash, and microbial quality; for non-parenteral oral dosage forms, USP 61/62 microbial enumeration and specified organism limits apply. Raft-forming oral suspensions contain sodium alginate with sodium bicarbonate and calcium carbonate; contact with gastric acid releases carbon dioxide and forms a low-density alginate raft. Tablet matrix performance depends on viscosity and particle size: high-viscosity grades at 2–5% of tablet mass retard drug release by forming a hydrated gel layer, but tablet hardness and dissolution must be validated under USP 711 dissolution apparatus conditions. Granulating solutions with viscosity above 1000 mPa·s can block 0.8 mm spray nozzles in wet granulation unless viscosity is controlled below 1000 mPa·s.
Reactive dye print pastes use sodium alginate over starch or guar because the alginate chain lacks primary hydroxyl groups and does not compete with dichlorotriazine or vinyl sulfone dye systems. Print pastes are prepared at 8–12% solids and exhibit pseudoplastic flow; after drying, the alginate film is washed out in cold water. Substitution with carboxymethylcellulose or guar lowers dye fixation and increases fabric stiffness after washing.
Cell immobilization systems based on droplet extrusion into 0.1 M CaCl₂ require high-G grades for bead mechanical stability. Bead diameter typically ranges from 2–4 mm; phosphate buffers above 20 mM sequester calcium and weaken alginate beads, requiring barium crosslinking or poly-L-lysine coating for long-term culture. High-M grades produce softer beads with faster diffusion but lower rupture strength; published data for specific cell-line configurations is limited.